Perhaps you should try some spelling variations:
dung ngan » dung nhan, dung luan
thu sach » tu sach, thuat sach, thuoc sach
nam dung » nam vung, nam dong, am dung
mai khoi » mai khoa, tai khoa, cac khoi
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
vai cac » va cac, tai cac, vay cac
voi cac » loi cach
va nam » van nam, ha nam, va nay

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ky nang ((mai khoi) or (ma hoa)). hieu va nam dung ngan hang ((vai cac) or (voi cac)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang ((mai khoi) OR (ma hoa)). hieu va nam dung ngan hang ((vai cac) OR (voi cac)) tren.
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang ((mai khoi) or (ma hoa)). hieu va nam dung ngan hang ((vai cac) or (voi cac)) tren*.